Changes in insecticide resistance of the rice striped stem borer (Lepidoptera: Crambidae).

Application of insecticides is the most important method to control Chilo suppressalis (Walker) (Lepidoptera: Crambidae), and continuous use of individual insecticides has driven the rapid development of insecticide resistance in C. suppressalis during the past 30 yr. Monitoring insecticide resistance provides information essential for integrated pest management. Insecticide resistance of field populations to monosultap, triazophos, chlorpyrifos, and abamectin in China was examined in 2010 and 2011. The results indicated that the resistance levels of 14 field populations to four insecticides were significantly different. Four populations showed moderate resistance, and other populations possessed low-level resistance or were susceptible to monosultap. Nine populations displayed an extremely high or a high level of resistance to triazophos, whereas four populations were sensitive to this agent. Five populations exhibited a low level of resistance to abamectin, while the others remained sensitive. When compared with historical data, resistance to monosultap and triazophos decreased significantly, and the percentage of populations with high-level or extremely high-level resistance was obviously reduced. By contrast, the resistance to abamectin increased slightly. The increasing and decreasing resistance levels reported in this study highlight the different evolutionary patterns of insecticide resistance in C. suppressalis. An overreliance on one or two insecticides may promote rapid development of resistance. Slow development of resistance to abamectin, which was used mainly in mixtures with other insecticides, implies that the use of insecticide mixtures may be an effective method to delay the evolution of resistance to insecticides.